Strand forming device



April 14, 1964 R. A. KERR 3,128,799

STRAND FORMING DEVICE Filed May 29, 1961 4 Sheets-Sheet 1 April 14, 1964R. A. KERR STRAND FORMING DEVICE Filed May 29, 1961 4 Sheets-Sheet 2RAKE/91? April 14, 1964 R. A. KERR 3,128,799

STRAND FORMING DEVICE Filed May 29, 1961 4 Sheets-Sheet 3 April 14, 1964R. A. KERR 3,128,799

STRAND FORMING DEVICE Filed ma 29. 1961 4'Sheecs-Sheet 4 m-- H MH WMH @HFW .MHE? a United States Patent Ofiice Patented Apr. 14, 1964 3,128,799STRAND FORMWG DEVICE Robert A. Kerr, Lachine, Quebec, Canada, assignorto Northern Electric Company, Limited, Montreal, Quebee, Canada, acorporation of Canada Filed May 29, 1961, er. No. 113,385 8 Claims.(til. 140-149) The present invention relates generally to the art ofmanufacturing stranded wire structures, and more particularly to theapparatus for preforming the individual component strands into thehelices they will assume in the finished cable.

Stranded wire structures, hereinafter referred to as cables, arecomposed of a plurality of elongated elements twisted or strandedtogether into helices of equal and constant pitch about a longitudinalaxis or a central core member. The individual elongated elements, orstrands, are either solid filaments or wires, or a plurality of solidwires stranded together similarly to the strands in the finished cable.The central core element, if used, may be solid or stranded wire, or afibrous rope. In electrical cables the strands may be individuallyinsulated by coverings of paper or other suitable material.

The cross-sectional shape of the individual component strands will varyin different cables. Concentric lay cables are usually composed ofstrands that are solid Wires or a plurality of stranded solid wires ofcircular cross-section. A cable that is constructed of circular wireswill, therefore, be referred to in this specification as a concentriclay cable, and its component strands as concentric strands.

Compact cables, which, because of their construction, contain the sameamount of material in a smaller crosssection than concentric lay cables,are manufactured by Winding sector-shaped component strands intolongitudinal helices in an assembled radial relationship such that theirflat sides are disposed radially to the central longitudinal axis of thefinished cable. The individual component strands are usually concentricstrands drawn through shaping dies or between pairs of shaping rolls tocompress the wires into the sector shape. These cables may or may nothave a central core member. One construction employs component strandsof a keystone shape that provide a hollow core for admission ofpressurized oil.

In order that the finished cable will not exhibit tendencies to coil ortwist, or that the individual strands will not unravel should the cablebe severed, it is common practice to preform the strands separately intothe required helices prior to their being laid into the finished cable.Prior art methods show this preforming to be done either before or afterthe individual strands have been placed in the cable forming machine.The preferred method is to preform the strands after they have beenplaced in the cable forming machine and as they are being laid into thecable because preforming them beforehand creates diiliculties in windingthe twisted strands onto the supply reels.

A common apparatus used for preforming circular strands and the sectorstrands of mechanical cables, consists of a cylindrical bar or quillindividual to each strand with a groove in the form of the desired helixmachined into its surface. Each quill is mounted in a close-fittingsleeve attached to the cable forming machine and the strands are drawnthrough their respective preforming passages defined by the helicalgrooves. Because the grooves are in the form of helices of constantpitch corresponding to the required helices of the strands in thefinished cable, these quills impose sudden twisting loads on the strandsas they enter the grooves and cause undue abrasion of the surfaces ofthe strands and the entrance surfaces of the grooves. Also, the powerrequired to pull the strands through these preforming passages is higherbecause of the sudden twisting loads than if the passages were designedto apply the twisting loads gradually.

In the manufacture of electrical cables from paper insulated sectorstrands a preferred form of the preforming apparatus consists of a splitdie individual to each of the strands with the preforming passage formedlongitudinally between the die halves. These passages also are in theform of helices of constant pitch and have the same effect on thestrands as those of the quills men.- tioned above, except that in thiscase the layers of insulating paper are subjected to the frictionaldamage. Lubrication of the strands may be employed to reduce the eifectsof the frictional forces, but on the paper insulated strands, even ifthe oil is that with which cables of this type are subsequentlyimpregnated, it provides a sticky surface to which undesirable foreignparticles may adhere. Other forms of insulation may be adverselyaffected directly by the application of a lubricant.

It is, therefore, the object of the invention to provide on the cableforming machine forming dies for each of the individual strands whichwill preform them into the desired longitudinal helices without imposingundue twisting loads or sudden changes in loads.

Another object of the invention is to provide forming dies that willreduce the amount of power heretofore re quired to preform the strands.

A further object is to provide forming dies that will not makelubrication necessary for smooth passage of the strands therethrough.

These and other objects are accomplished by providing for each strand apassageway formed either between two halves of a die or in the surfaceof a quill such that the passageway is a helix of infinite pitch, thatis, a straight line, tangential to the strand at the entrance end, anddecreasing pitch toward the exit end such that a strand passingtherethrough will emerge from the exit end in the form of the helixrequired for proper laying-in of the strand into the finished cable.

A complete understanding of the invention may be obtained from thefollowing detailed description and 'explanation which refer to theaccompanying drawings, illustrating preferred embodiment in which likereference numbers refer to like parts, and in which:

FIG. 1 is a diagrammatic side elevation of a cable forming machinehaving this invention embodied therein;

FIG. 2 is a sectional view of a compact cable formed of sector strands;

FIG. 3 is a side elevation of one embodiment of a forming die mounted onthe cable forming machine of FIG. 1;

FIG. 4 is an end elevation of the forming die of FIG. 3;

FIG. 5 is a perspective view of a forming die insert;

FIGS. 6, 7 and 8 are sections taken along lines 6-6 7-7 and 88respectively in FIG. 5;

FIG. 9 is a perspective view of a forming die cap inverted from itsposition in the forming die of FIG. 4;

FIG. 10 is a sectional View of a concentric lay cable formed ofconcentric strands;

FIG. 11 is a partial side elevation of another embodiment of a formingdie;

FIG. 12 is an end elevation of the forming die of FIG. 11;

FIG. 13 is a perspective view of a quill .for the forming die of FIG.1'1; and

FIGS. 14, 15 and 16 are sections taken along lines 1414, 15-15 and 1'616respectively in FIG. 13.

In FIG. 1 is illustrated a cable forming machine which comprises acentral tubular shaft 1 supported at one end by a bearing 2 mounted on apedestal 3, and at the other end by freely rotatable rollers 4 adaptedto contact the cylindrical surface of a strand guide plate 5. Attachedto shaft 1 is a reel support plate 6 to which are mounted reel cradles7. In this embodiment four cradles are equally spaced around and at thesame distance from the shaft 1, two of which have been deleted in theillustration for clarity. One supply reel 8 is rotatably mounted in eachcradle 7 by means of the arbor 9. Also mounted on shaft 1 is a formingdie plate 10 additionally supported by rollers 11 rotatably mounted in ahousing 12. Rotation of the forming machine about its axis is achievedby a driving means (not shown) through gear 13 rigidly attached to therearmost end of shaft 1.

In the manufacture of a compact cable the sector strands 14 are coiledon the supply reels 8. As shown in FIG. 2 the cross-section of thesector strand 14 is bounded by two intersecting fiat surfaces 15 and anarcuate surface 16. When the machine is in operation the individualsector strands 14 are drawn from the reels 8 through apertures in theguide plate 5 and through separate forming dies '17, to which thisinvention is directed, attached to the forming die plate 10, equallyspaced around and at the same distance from the shaft 1. The formingdies 17 impart a twist to each sector strand 14 to assist in thelaying-in of these strands as they converge at a closing die 18 to forma compact cable 19 of crosssectional shape as shown in FIG. 2. The cableis drawn from the forming machine and coiled by a suitable capstan andtake-up indicated generally as the haul-01f mechanism 21' supported onstand 22'. The rate at which the capstan draws the sector strands 14from the reels 8, coupled with the rotary speed of the forming machinedetermines the helical pitch or lay of the strands in the assembledcompact cable 19. If desired a central core wire may be supplied throughthe tubular bore of the central shaft 1 from a reel 21 mounted on astand 22.

FIGS. 3 and 4 show in detail one embodiment of a forming die 17 adaptedespecially for the sector strand 14. Attached to the forming die plate10 by means of a backing plate 23 and screws 24 is an adaptor plate 25suitably constructed to provide a mounting surface 26 substantiallynormal to the sector strand 14. To the surface 26 is mounted a dieholder 27 by means of cap screws 28 passing through arcuate slots 20 inthe mounting flange 30. When the cap screws 28 are loosened the slots 29permit rotation of the die holder 27 about its longitudinal axis bymeans of a prying bar inserted in a hole 31 passing through a tab 32.The backing plate 23, forming die plate 10, adaptor plate 25, and themounting flange of the die holder 27 have an aperture 33 extendingthrough them to permit passage of the sector strand 14 therethrough tothe forming portion of the die.

The portion of the forming die 17 in which the sector strand 14 istwisted into the desired helix consists of a die insert 34 and a die cap35 held in co-operating relationship within a seat in the saddle portion36 of the die holder 27. The elongated die insert 34 is adapted for asliding fit within the seat which is formed by the parallel side walls37 and a lower surface 38 extending at right angles between them. Thedie insert 34 is secured against movement within the seat by means ofcap screws 39. The (to-operating die cap 35 has an extended portionbetween the parallel edges adapted for a sliding fit within the sidewalls 37 of the saddle portion 36, and is held in position by wingscrews 31 extending through longitudinal horizontally extending tabs 42.

A passage within which the sector strand 14 is twisted lies between andlongitudinally of the die insert 34 and die cap 35. Thatportionof thepassage which is formed in the die insert 34 is more clearly shown inFIGS. 5 to 8 inclusive. At any cross-section of the die insert 34 suchas at line '66 in FIG. 5, the groove is V-shaped as defined by the sidewalls 43 inclined with respect to each other at an angle at whichcorresponds to the angle between the fiat surfaces 15 of the sectorstrand 14. The intersection of the side walls 43 forms a straight lineAA that extends normal to the cross-section of the die insert 34 in aplane the edge view of which, as represented by line BB in FIG. 6,bisects the cross-section. The widths of the side walls 43 are equal toeach other and to the width of a flat surface 15 of the sector strand14. As shown the upper edges of the side walls 43 are formed byintersections with the surfaces 44 and 45 respectively which surfaces inthe cross-sectional plane extend parallel to the lower surface 46 of thedie insert 34.

The twist is imparted to the sector strand 14 by changes in the angularposition of the groove cross-section in one rotational direction aboutthe line AA between the entrance end 47 and the exit end 48 of the dieinsert 34. This change in angular position is shown in FIGS. 6 to 8 bythe rotation of the bisector CC of the angle at of the V-shaped groovethrough an angle 0 which determines the total amount of twist applied tothe sector strand 14. Because it is impractical to rotate the groovebeyond the point where either of the side walls 43 becomes parallel tothe lower surface 46, a maximum twist angle 0 is obtained byconstructing the groove with the bisector CC at the entrance end 47 anangle to one side of the line BB and at the same angle to the other sideat the exit end 48. The direction of rotation of the bisector CCdetermines the lay direction of the sector strand 14 in the finishedcompact cable 19.

At any intermediate cross-section of the die insert the bisector CC isat some angle 0 less than the final angle 0, to its original position atthe entrance end 47 as now represented by line D-D in FIG. 7. This angle0 determines the twisting force or torque applied to the sector strand14 at that point a distance x from the entrance end 47. In thisinvention the angles fi at the cross-sections throughout the length ofthe die insert are such that the torque T on the sector strand 14increases from zero, or a very low value, at the entrance end 47 to amaximum value T at the exit end 48 proportionally to the distance x fromthe entrance end 47. In a die insert of length D, therefore,

The relation between the torque T and the angle 0 is obtained from theequation for a cylindrical bar of length I under a constant torque Tabout its longitudinal axis:

Tl e? where 0 is the angle through which the sector strand is twistedand G and I represent physical constants for the particular sectorstrand. This equation may be rewritten as T=GJ Equation I from which itis apparent that the torque is proportional to the rate of change of theangle of twist of the sector strand. For the groove of this invention inwhich the torque on the sector strand '14 is increased evenly, asimplified form of the above expression for any point along the dieinsert a distance x from the entrance end 47 is d0, T or'czg lAt theexit end 48 the rate of change of the angle 0 is determined from thehelical pitch or lay of the com- Equation II pact cable 19 in which thesector strand 14 twists through 360 in a distance L. This rate of changeis nan! dw L From Equations I, II and III the rate of change of theangle 0,, is

Equation III E5 D X L for the torque T to increase evenly over the dieinsert of length D. Integration of Equation IV gives Equation IV ExampleA plurality of sector strands 14 are to be assembled into a compactcable with a 60 inch right-hand lay, that is, each strand will form ahelix with a clockwise twist and a pitch of 60 inches. The forming dieinserts 34 are inches long. The equation for the angular position of thegroove at any distance x from the entrance end 47 of the die insert 34is, from Equation V above,

The total twist 0 of the groove is determined at the exit end 48 wherethe distance x equals the length D of the die insert 34. Its value inexample is The groove, therefore, will begin 15 degrees to the left ofthe line BB at the entrance end 47 and rotate through degrees clockwiseto 15 degrees to the right of line BB at the outlet end 48. The distancefrom the entrance end 47 to the point where line B-B and bisector CCcoincide, or, in other words, to where bisector CC has rotated through15 degrees, is, again from Equa- The portion of the passage between thedie insert 34 and die cap 35 that is formed within the die cap 35 andco-operates with the V-shaped groove in the die insert 34 to impart thedesired twist to the sector strand 14 is shown in FIG. 9. The groove isarcuate in cross-section as shown at 49, the radius of curvaturecorresponding to that of the arcuate surface 1 6 of the sector strand14. When the die cap 35 is in co-operating relationship with the dieinsert 34 the surface 49 at any cross-section has its center ofcurvature on the line A-A of the die insert 34 and is disposed angularlyabout the line A-A such that the lines of intersection between thesurface 49 and the surfaces 50 and 51 are adjacent the aforementionedlines of intersection of the side walls 43 and the surfaces 44 and 45respectively of the V-shaped groove in the die insert 34. These surfaces50 and 51 are disposed at right angles to the side walls of the die cap35 and contact throughout their surface are as the surfaces 44 andrespectively of the die insert 34.

In this embodiment of the forming die 17 a die insert 34 and a die cap35 are necessary for each size and lay of the sector strand 14. When theproper die insert 34 and die cap 35 are assembled about a sector strand14 in a cable forming machine, the die holder 27 is rotated Equation V 6about the longitudinal axis of the sector strand 14 by means of a pryingbar inserted in the hold 31 in the tab 32, as hereinbefore described, toposition the sector strand 14 so that its flat surfaces 15 are disposedradially to the longitudinal axis of the compact cable I1 9 at theclosing die 18.

Another embodiment of a forming die 17 is shown in FIGS. 11 and 12 andis particularly adaptable to the manufacture of concentric lay cables, atypical form of which is shown in FIG. 10. This cable 52 is composed ofconcentric strands 53 substantially circular in crosssection, strandedin close relationship about a central core strand 54. The forming die 17for preforming these concentric strands 53 is substantially the same ashereinbefore described for the sector strands 14 except that the formingportion consists of a cylindrical quill 55 having a groove 57 in itscylindrical surface 58 of U-shaped cross-section adapted to accept theconcentric strand 53 in a close-fitting but slidable relationship.

The quill 55 is secured against movement within a close fittingconcentric sleeve 56 by cap screws 59. The combination of the quill 55and sleeve 56 is fixed rigidly by cap screws 60 within a concentric seat61 formed in a saddle portion 62 of a die holder 63 and lies coaxiallywith respect to the longitudinal axis of the concentric strand 53. Thedie holder 63 is the same as the die holder 2.7 of FIGS. 3 and 4 exceptfor the saddle portion 62. The quill 55, sleeve 56 and saddle portion62. constitute the forming portion of the second embodiment of theforming die 17.

The quill 55 as shown in FIG. 13 is constructed of such diameter and thegroove 57 of such depth that the concentric strand 53 will lie justcompletely within the groove 57 and that in this position thelongitudinal axis of the concentric strand 53 is the same radialdistance from the longitudinal axis of the quill 55 as it would be fromthe longitudinal axis in the finished concentric lay cable 52. Also theangular position of the groove 57 about the longitudinal axis of thequill 55 and between the entrance end '64 and the exit end 65 thereof isdetermined by the previously developed Equation V. A typical position ofthe groove 57 at the entrance end 63 is shown in FIG. 14, and at theexit end 65 in FIG. 16 after rotating counterclockwise through a totaltwist angle 0. FIG. 15 shows the groove 57 at a point a distance x fromthe entrance end 64 after having rotated through angle 0 In thesefigures the line BE represents the position of the groove 57 at theentrance end 64 and line F-F, the position at any other point in thelength of the quill 55. In this embodiment there is no restriction onthe total twist angle 0 for the groove 57. A separate combination ofquill 55 and sleeve 56 is required for each particular diameter and layof the concentric strand 53, and for different radial distances of thesestrands from the longitudinal axes in various concentric lay cables 52.

Although this embodiment is particularly suited for concentric strands53 it is also adaptable for other strand shapes such as the sectorstrand 14. For these applications in which the sector strands 114 mustbe properly aligned at the closing die 18, the die holder 63 may berotated about its longitudinal axis similarly to the die holder 27 ofFIG. 3 by means of a prying bar inserted in a hole 66 formed in the tab67.

Either form of the twisting passage described in the two embodiments ofthe invention may be modified to over-twist the component strand so thatif there is any relaxation of the twist in the strand as it leaves thepassage the added twist will compensate and the strand will assume therequired form. The amount of added twist will be specific for each sizeand material of the strand, and for each lay of the strand in thefinished cable. It may be determined experimentally and decreases thehelical pitch L in Equation V to less than the actual value for thecable, resulting in an increase in the twist angle 0.

Although only two embodiments of the invention have been described, itwill be apparent that other adaptions and modifications will be possiblewithin the scope of the following claims.

What is claimed is:

1. In an apparatus for making a stranded wire structure from a pluralityof component strands which comprises a rotary cable forming machine, a'closing die adjacent the outlet end thereof, a haul-off mechanismadjacent said closing die 'for pulling the stranded Wire structurethrough said machine and said closing die; a forming die plate includedin said machine and rigidly attached to the output end thereof,havingaflixed thereto a forming die individual to each of said strands,a longitudinal passage formed in said forming die adapted to engage andimpart a twist to said strand, said passage at the entrance end thereofbeing a helix of infinite pitch, tangential to said strand, and havingthe form of a helix at the exit end thereof corresponding to the helixof said strandin said stranded wire structure,'said passage beingsmoothly transitional between said entrance and said exit ends thereofin the form of a helix of progressively decreasing pitch.

2. In an apparatus'in accordance with claim 1 wherein said formingdieincludes a' die holding means, a die insert, and a co-operating'diecap.

3. In an apparatus in accordance with claim 2 said die insert with alongitudinal groove formed within one surface thereof, said groovedefined by two side walls disposed with respect to each other at anangleequal to the angle'betwee'n the flat surfaces ofsaid sector-shapedstrand, said side walls intersecting along a straight line parallel tothe longitudinal axis of said die insert, the position of said groovealong the length of said die insert defined by rotation of said sidewalls about said line of intersection according to the expression where9,, 'is the angle through which said side walls rotate in a distance xmeasured from one end of said die insert, D is the lengthof said dieinsert, L is the helical pitch of said strand in said stranded wirestructure; and said die cap with a longitudinal groove therein having anarcuate cross-section with a radius of curvature equal to that of thearcuate surface of said strand, said die cap co-operating with said dieinsert to form said longitudinal passage therebetween.

4. In an apparatus in accordance with claim 2 saiddie holding meanscomprising a flange, a saddle portion having a rectangular groovetherein and having means for rigidly positioning said die insert andsaid die cap in co-operating relationship with said longitudinal passageextending perpendicularly to said flange, said flange having a centralaperture to permit passage of said strand therethrough to saidlongitudinal passage, arcuate slots positioned adjacent to and lyinginside the outer periphcry of said flange for passage therethrough ofmounting screws into said forming die plate, said slots'permittingrotation of said forming die with respect to said forming die plateabout the longitudinal axis of said strand.

5. In an apparatus in accordance with claim 1 said forming die includinga die holding means, a cylindrical 8 quill anda concentric sleevepositioned coaxially within a cylindrical seat in said die holdingmeans, said longitudinal passages formed within the surface of saidquill adapted to engage and impart a twist to said strand, said passageat the entrance end thereof being a helix of infinite pitch, tangentialto said strand, and having the form of a helix at the exit end thereofcorresponding to the helix of said strand in said stranded wirestructure, said passage being smoothly transitional between saidentrance and said exit ends in the form of a helix of progressivelydecreasing pitch.

6. In an apparatus in accordance with claim 5 said quill with alongitudinal groove in the cylindrical surface thereof, said grooveadapted to receive said strand therein in a close slidable relationship,the position of said groove along the length of said quill defined bythe rotation of the cross-section of said groove about the longitudinalaxis of said quill according to the expression where 0 is the anglethrough which said cross-section rotates in a distance 2: measured fromone end of said quill, D is the length of said quill, L is the helicalpitch of said strand in said stranded wire structure; and said sleeveco-operating coaxially with said quill to form said longitudinal passagetherebetween.

7. In an apparatus in accordance with claim 6 said die holding meanscomprising a flange, a saddle portion having a cylindrical seat thereinand having means for rigidly positioning said quill and said sleeve incoaxial co-operating relationship with the longitudinal axis of saidquill extending perpendicularly to saidflange, said flange having acentral aperture to permit passage of said strand therethrough to saidlongitudinal passage, arcuate slots positioned adjacent to and lyinginside the outer periphery of said flange for passage therethrough ofmounting screws into said forming die plate, said slots permittingrotation of said forming die with respect to said forming die plateabout the longitudinal axis of said strand.

8. A forming die for imparting a uniform twist to a wire strandcomprising; a die body, a longitudinal passage formed in said die bodyand adapted to engage and impart a twist to said strand, said passage atthe entrance end thereof being a helix of infinite pitch, tangential tosaid strand, and having the form of a helix at the exit end thereof withapitchdesired in the finished strand, the portion of said passagebetween said entrance and said exit ends having the form of a helix ofprogressively decreasing pitch from the infinite pitch of said entranceend to the pitch of said exit end, whereby a strand passing through saiddie body will be subjected to an evenly increasing amount of torque forimparting a twist to said strand.

References Cited in the file of this patent ,UNITED STATES PATENTS152,557 Haskell et al June 30, 1874 1,243,353 Snedeker Oct. 16, 19171,761,482 Laubenthal June 3, 1930 2,218,104 Brignall Oct. 15, 1940

1. IN AN APPARATUS FOR MAKING A STRANDED WIRE STRUCTURE FROM A PLURALITYOF COMPONENT STRANDS WHICH COMPRISES A ROTARY CABLE FORMING MACHINE, ACLOSING DIE ADJACENT THE OUTLET END THEREOF, A HAUL-OFF MECHANISMADJACENT SAID CLOSING DIE FOR PULLING THE STRANDED WIRE STRUCTURETHROUGH SAID MACHINE AND SAID CLOSING DIE; A FORMING DIE PLATE INCLUDEDIN SAID MACHINE AND RIGIDLY ATTACHED TO THE OUTPUT END THEREOF, HAVINGAFFIXED THERETO A FORMING DIE INDIVIDUAL TO EACH OF SAID STRANDS, ALONGITUDINAL PASSAGE FORMED IN SAID FORMING DIE ADAPTED TO ENGAGE ANDIMPART A TWIST TO SAID STRAND, SAID PASSAGE AT THE ENTRANCE END THEREOFBEING A HELIX OF INFINITE PITCH,